The Collaborative International Dictionary of English v.0.48:

Mass \Mass\, n. [OE. masse, F. masse, L. massa; akin to Gr. ? a
   barley cake, fr. ? to knead. Cf. Macerate.]
   [1913 Webster]
   1. A quantity of matter cohering together so as to make one
      body, or an aggregation of particles or things which
      collectively make one body or quantity, usually of
      considerable size; as, a mass of ore, metal, sand, or
      water.
      [1913 Webster]

            If it were not for these principles, the bodies of
            the earth, planets, comets, sun, and all things in
            them, would grow cold and freeze, and become
            inactive masses.                      --Sir I.
                                                  Newton.
      [1913 Webster]

            A deep mass of continual sea is slower stirred
            To rage.                              --Savile.
      [1913 Webster]

   2. (Phar.) A medicinal substance made into a cohesive,
      homogeneous lump, of consistency suitable for making
      pills; as, blue mass.
      [1913 Webster]

   3. A large quantity; a sum.
      [1913 Webster]

            All the mass of gold that comes into Spain. --Sir W.
                                                  Raleigh.
      [1913 Webster]

            He had spent a huge mass of treasure. --Sir J.
                                                  Davies.
      [1913 Webster]

   4. Bulk; magnitude; body; size.
      [1913 Webster]

            This army of such mass and charge.    --Shak.
      [1913 Webster]

   5. The principal part; the main body.
      [1913 Webster]

            Night closed upon the pursuit, and aided the mass of
            the fugitives in their escape.        --Jowett
                                                  (Thucyd.).
      [1913 Webster]

   6. (Physics) The quantity of matter which a body contains,
      irrespective of its bulk or volume.
      [1913 Webster]

   Note: Mass and weight are often used, in a general way, as
         interchangeable terms, since the weight of a body is
         proportional to its mass (under the same or equal
         gravitative forces), and the mass is usually
         ascertained from the weight. Yet the two ideas, mass
         and weight, are quite distinct. Mass is the quantity of
         matter in a body; weight is the comparative force with
         which it tends towards the center of the earth. A mass
         of sugar and a mass of lead are assumed to be equal
         when they show an equal weight by balancing each other
         in the scales.
         [1913 Webster]

   Blue mass. See under Blue.

   Mass center (Geom.), the center of gravity of a triangle.


   Mass copper, native copper in a large mass.

   Mass meeting, a large or general assembly of people,
      usually a meeting having some relation to politics.

   The masses, the great body of the people, as contrasted
      with the higher classes; the populace.
      [1913 Webster]

WordNet (r) 3.0 (2006):

mass meeting
    n 1: a large gathering of people intended to arouse enthusiasm
         [syn: rally, mass meeting]